Piezoelectric reading of ferroelectric data storage media

ABSTRACT

An apparatus comprises mechanically scanned ferroelectric data storage media. A scanning electrode contacts the scannable surface with a contact force. The ferroelectric data storage media generates a piezoelectric potential that is picked up by the electrode. The piezoelectric potential has a polarity that varies as a function of data polarity on the data storage media.

FIELD

The present invention relates generally to ferroelectric data storagemedia, and more particularly but not by limitation to non-destructivelyreading of ferroelectric data storage media with an electrode array.

BACKGROUND

Known ferroelectric readback methods are either excessively complex andcostly or inherently erase data that is being read. In ferroelectricstorage devices, information is stored in ferroelectric domains. Forwriting data into the ferroelectric material, small ferroelectricdomains are formed by locally applying an electrical field with a verysmall tip. For reading the data back, various methods are available,including piezo-force-microscopy (PFM),scanning-nonlinear-dielectric-microscopy (SNDM), and erase read-back(ERB). All three methods have certain disadvantages for the electrodestorage application. PFM and SNDM both require complicated measurementinstruments. PFM requires an atomic force microscopy (AFM) like setup tomeasure the very small height change, whereas SNDM requires a microwaveresonator, an oscillator and a FM demodulator to measure the localdielectric response. ERB senses the polarization currents by switchingall domains into one polarization state, which erases the storedinformation. Therefore after reading the data, the data must berewritten.

A method and apparatus are needed for reading data from ferroelectricstorage media without erasing the data and without complex, expensive,high power readback mechanisms. Aspects of the present invention providesolutions to these and other problems, and offer other advantages overthe prior art.

SUMMARY

Disclosed is an apparatus that comprises ferroelectric data storagemedia with a scannable surface. The apparatus comprises an electrodecontacting the scannable surface with a contact force. The ferroelectricdata storage media generates a piezoelectric potential that is picked upby the electrode. The piezoelectric potential has a polarity that variesas a function of data polarity on the data storage media.

In one aspect, the piezoelectric potential comprises a basebandpotential. In another aspect, the contact force is modulated, and thepiezoelectric potential comprises a modulated piezoelectric potential.

Other features and benefits that characterize aspects of the presentinvention will be apparent upon reading the following detaileddescription and review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C illustrate a ferroelectric data storage drive that isscanned by an electrode array.

FIGS. 2A, 2B illustrate a data storage apparatus 200 sensing basebandpiezoelectric potentials.

FIG. 3 illustrates a block diagram of a data storage apparatus sensingmodulated piezoelectric potentials.

FIG. 4 illustrates a timing diagram corresponding generally with FIG. 3.

FIG. 5 illustrates a block diagram of a data storage apparatus thatincludes shielding, digital filtering and phase synchronous detection.

FIG. 6 illustrates a graph of charges that are producedpiezoelectrically.

DETAILED DESCRIPTION

In the aspects described below, a ferroelectric data storage layer isscanned with an electrode. A force (pressure) is applied to theelectrode. There is a piezoelectric response in the ferroelectric datastorage layer to the pressure of an electrode tip placed in directcontact on the surface of the ferroelectric material. The piezoelectricresponse is used to sense a polarization state of the data storage layerunder the electrode tip. When this tip moves over the surface whilemaintaining the pressure, and passes along differently polarized regionsof the data storage layer, the piezoelectric effect produces apiezoelectric signal. The polarity or phase of the piezoelectric signalcorresponds to the polarization state of the region underneath the tip.The data stored on the ferroelectric data storage layer can be read as apiezoelectric voltage without erasing the data and without the use ofapparatus that is excessively complex, delicate and costly to be used ina data storage device.

The amount of charge produced by the piezoelectric effect is quitesmall. Direct (baseband) detection with a relatively constant electrodeforce and simple amplifier and detection circuits can be used asillustrated in FIGS. 2A, 2B. Alternatively, the mechanical force on thescanning electrode can be a modulated force, and a lock-in detectiontechnique can be used to decrease error rates as described below inconnection with an example illustrated in FIGS. 3, 4, 5. If the appliedpressure is modulated with a specific frequency, the generatedelectrical signal will also exhibit this frequency. At the interfacebetween two different polarization states, a 180° phase jump of theelectrical signal to the excitation signal will occur, which is detectedby the lock-in technique.

FIG. 1A illustrates an exemplary ferroelectric data storage drive 10 inwhich aspects of the invention are useful. The drive 10 comprises aferroelectric storage medium 16 with a scannable surface 12. An array ofelectrodes 14 contact the scannable surface 12 and communicate data toand from the scannable surface 12. Microactuators such as microactuator20 provide relative scanning motion between the scannable surface 12 andthe electrodes 14. Electrical contacts 18 provide connections betweenthe drive 10 and a host computer system.

FIGS. 1B-1C illustrate an array 100 of sensing contact electrodes 102,104, 106, 108, 110, 112 that are formed in cavities of a substrate 114.FIG. 1B illustrates a top (plan) view of the array 100, and FIG. 1Cillustrates a front cross-sectional view taken along line 1C-1C in FIG.1B.

The substrate 114 provides a common electrode support for the sensingcontact electrode 102, 104, 106, 108, 110, 112. Substrate 114 is onlypartially shown in FIGS. 1B, 1C and can extend to support a largernumber of sensing contact electrodes that are not illustrated in FIGS.1B, 1C. The sensing contact electrodes 102, 104, 106, 108, 110, 112 arepreferably arranged in a regular rectangular array, as illustrated, orin oblique alignments. The substrate 114 is movable relative to asurface 116 (FIG. 1C) along X and Y axes to provide scanning of thesurface 116 by the sensing contact electrodes 102, 104, 106, 108, 110,112. The substrate 114 is also movable by a microactuator (notillustrated in FIGS. 1B-1C) to move along a Z axis relative to theferroelectric medium surface 116. The controlled spacing Z is typicallyselected to provide a desired force preload magnitude between thesurface 116 and each of the sensing contact electrodes. The preloadforce deflects the sensing contact electrodes 102, 104, 106, 108, 110,112 so that the sensing contact electrodes 102, 104, 106, 108, 110, 112preferably function as springs. Relative motion between the substrate114 and the surface 116 can be effected by motion of the substrate 114,motion of the surface 116, or motion of both the substrate 114 and thesurface 116. The preload force can be continuously maintained (asdiscussed below in connection with FIGS. 2A, 2B) or, alternatively, thepreload force can include a time varying component along a Z axis (asdiscussed below in connection with FIGS. 3, 4, 5).

Substrate 114 and surface 116 are illustrated as flat elements in FIGS.1B-1C, however, the substrate 114 and the surface 116 can have othershapes such as round cylindrical shapes. The surface 116 comprises asurface of a ferroelectric memory that is accessed by the electrodes102, 104, 106, 108, 110, 112. Relative motion between the substrate 114and the surface 116 can be any suitable scanning motion such as randomaccess scanning, raster scanning, or other known surface scanningmotions or patterns. With the use of multiple electrodes, a large numberof bits of data can be written or read simultaneously (in parallel) toprovide high speed access.

Exemplary conductor leads 118, 120, 122 run over a top surface 115 ofthe substrate 114 to carry information to and from the sensing contactelectrodes 108, 110, 112. The conductor leads 118, 120, 122 couple toelectronic circuitry (not illustrated) that can be located on thesubstrate surface 115 or elsewhere.

An exemplary sensing contact electrode such as sensing contact electrode110 comprises a beam support 124 (a portion of the substrate 114) and anelectrode 126. The electrode 126 comprises a bent beam body 128extending from the beam support 124 to an electrode tip face 130 spacedapart from the beam support 124. The aspects illustrated in FIGS. 1A,1B, 1C are illustrative, and other known electrode and data storagescanning arrangements can also be used as well.

FIG. 2A illustrates a block diagram of a data storage apparatus 200. Thedata storage apparatus 200 comprises data storage media 202 with ascannable surface 204. A layer (or substrate) 210 underlies the datastorage media 202. The layer 210 is electrically conductive and servesas a reference potential (common return) for the data storage media 202.Other known arrangements for obtaining a reference potential offerroelectric storage media can be used as well. The data storage media202 and the layer 210 are illustrated in cross-section in FIG. 2A. Inone aspect, the scannable surface 204 comprises a generally flat surfaceas illustrated. In other aspects, the scannable surface 204 comprises acylindrical surface, a tape surface or other known media surface shape.The scannable surface can include a lubricant layer or other known mediainterface layers.

The storage media 202 comprises a ferroelectric material. The storagemedia 202 comprises storage media elements 212, 214, 216, 218, . . . ,220 that are selectively polarized in an up or down direction to storedata. An up arrow 222 indicates a first ferroelectric polarization(logical one) and a down arrow 224 indicates a second ferroelectricpolarization (logical zero) of the stored data. The ferroelectricpolarization is non-volatile, but electrically alterable so that thestorage media 202 can be used as reusable data storage media.

An electrode 206 includes an electrode tip 208 that electricallycontacts the scannable surface 204 with a mechanical contact force 207.The mechanical contact force 207 at the scannable surface 204 produces amechanical stress in the data storage media 202 under the electrode tip208. The storage media 202, in addition to comprising ferroelectricproperties, also comprises piezoelectric properties. The storage media202 generates a piezoelectric voltage responsive to the appliedmechanical contact force 207. The piezoelectric voltage has a polaritythat is a function of the force and is also a function of the directionof the ferroelectric data polarization. A logical one provides a firstpolarity of piezoelectric voltage, and a logical zero provides a secondopposite polarity of piezoelectric voltage due to the mechanical contactforce. The polarity of the piezoelectric voltage is controlled by thedirection of polarization of the storage media 202 or, in other words,controlled by the logic state of the stored data.

The electrode 206 and the scannable surface 204 move relative to oneanother with a scanning motion so that the electrode mechanically scansthe scannable surface 204. The scanning motion is controlled by a servocontrol system so that the electrode tip 208 sequentially passes over aselected sequence of storage media elements such as storage mediaelements 212, 214, 216, 218, . . . , 220. In one aspect, the scanningmotion includes a spinning disc media and a servo controllable electroderadius on the disc media. In another aspect, the scanning motionincludes X positioning of the electrode 206 and Y positioning of thescannable surface 204 under servo controls. As the electrode scansacross a sequence of storage media elements 212, 214, 216, 218, . . . ,220, the electrode tip 208 senses the piezoelectric voltage of each dataelement relative to a reference potential of the layer 210. The term“scanning” used here refers to accessing data stored on media byrelative mechanical motion between an electrode and a media surface, anddoes not refer to switching an array of electrical conductors instationary contact with media.

The electrode tip 208 mechanically scans the storage media data elements212, 214, 216, 218, . . . , 220 in an X direction 226 at a scanningspeed to produce a time sequence of data bits that are piezoelectricvoltages, but that represent the data stored by ferroelectric storage.The mechanical scanning speed in bits per second is referred to hereinas a baseband data rate.

The electrode 206 is coupled by a lead 230 to an amplifier 232. Theamplifier 232 may be positioned remote from the electrode 206 or may bepositioned on the electrode 206 so that the amplifier 232 moves with theelectrode 206. Positioning the amplifier 232 on the electrode 206provides an advantage of reduced stray capacitive loading of thepiezoelectric voltage. Positioning the amplifier remotely avoids theproblem of connecting multiple flexible conductors to support theamplifier 232 on the moving electrode 206. The amplifier 232 amplifiesthe piezoelectric voltage at electrode 206. In one aspect, the amplifier232 provides voltage gain. In another aspect, the amplifier 232comprises a unity gain amplifier that buffers the low power, highimpedance piezoelectric electrode voltage to provide a lower impedance,higher power amplifier output 234.

The amplifier 232 provides an amplifier output 234 to a piezoelectricpotential detector 236. Potential detector 236 provides a potentialdetector output 238. The potential detector output 238 preferablycomprises a digital output that represents the polarity of the scannedsequence of data bits. It will be understood by those skilled in the artthat detecting the polarity of piezoelectric potential with reference toa clock signal representing the baseband scanning rate can also bedescribed as baseband phase detection. Potential detector 236 can thusalso be seen as a baseband phase detector.

In one aspect, the potential detector 236 comprises an autosynchronouspotential detector. The autosynchronous phase detector uses the incomingbaseband data itself to provide an internal phase reference for phasedetection synchronization. In one aspect, the stored data includespreambles for improving synchronization. In a further aspect, the storeddata is encoded with run length limited encoding or other encoding toimprove synchronization. In one aspect, the phase detector output 238represent polarities, and is connectable to a read channel that decodesthe polarities. In another aspect, the baseband phase detector output238 represents phase transitions, and is connectable to a read channelthat decodes the phase transitions. In yet another aspect, the basebandphase detector 236 receives a phase reference from electrode positionsensor (not illustrated) mounted on the electrode 206.

While the circuitry shown in FIG. 2A has been describe above in terms ofanalog signal processing, it will be understood by those skilled in theart that the circuitry shown in FIG. 2A can alternatively be implementedin terms of other known circuitry. The amplifier 232, for example, canbe implemented with bitstream or delta sigma circuits and the amplifieroutput 234 can comprise a digital data stream at a bit rate that ishigher than the baseband data rate. In such an alternative circuittechnology, the phase detector 236 processes a digital data stream toprovide polarity detection or phase detection.

The polarity detector output 238 is connectable to a read channel thatincludes features such as error detection and correction decoding toprovide a useful readback signal to a host computer system. The contactforce 207 can be provided by a spring in an electrode suspension system,or can be actively controlled by a force control system to a constantvalue during reading. The contact force 207 is preferably constantduring readback intervals of data. The contact force 207, however, canbe reduced during write intervals when a lower contact force is adequatefor writing.

FIG. 2B illustrates an exemplary timing diagram for the apparatus 200shown in FIG. 2A. As the electrode 206 moves in the direction 226 on thesurface 204, a piezoelectric potential (voltage waveform) 242 isgenerated. The voltage waveform 242 has a polarity (baseband phase) thatcorresponds with the polarity of the data stored beneath the electrode206.

FIG. 3 illustrates a block diagram of a data storage apparatus 300. Thedata storage apparatus 300 is similar in many respects to the datastorage apparatus 200 in FIG. 2A. In FIG. 3, however, a mechanicalcontact force 307 is not constant, but instead includes an oscillatoryforce component (mechanical modulation) that oscillates during a timeinterval while an electrode tip 308 passes over a single storage mediaelement such as storage media elements 312, 314, 316, 318, . . . , 320.In one aspect, the mechanical contact force 307 includes a constantforce component and an oscillatory or modulated mechanical forcecomponent. The modulated force component includes at least one frequencycomponent that has a higher frequency than the baseband data ratefrequency (described above in connection with FIG. 2A). In one aspect,the modulated force component has a predominant modulation that isgenerally sinusoidal, has a substantially fixed frequency for anyparticular read operation, and is referred to here as a “mechanicalmodulation frequency” or “carrier”.

An electrode 306 scans a scannable surface 304 of data storage media 302that is supported on a layer 310 that is a common conductor for the datastorage media 302. Data is stored on the data storage media and an uparrow 322 indicates a logic one and a down arrow 324 indicates a logicalzero. During scanning in X direction 326, a piezoelectric voltage isproduced at an electrode tip 308. The piezoelectric voltage at electrodetip 308 includes a baseband component with a baseband polarity (basebandphase) determined by the constant mechanical force component and thelogical data state, as in FIG. 2A. The piezoelectric voltage atelectrode tip 308 includes a carrier component at the mechanicalmodulation frequency. The carrier polarity (carrier phase) of thecarrier is controlled by the logical data state. The piezoelectricvoltage at electrode tip 308 is coupled along line 330 to amplifier 332.

In one aspect, amplifier 332 comprises a narrowband filter with apassband centered around the carrier frequency. The modulation processis mechanical, and the carrier frequency is somewhat variable. In oneaspect, the amplifier 332 includes a tracking filter to track variationsin the carrier frequency, the bit rate or both. The amplifier 332provides an amplifier output 334 to a phase detector 336. The phasedetector 336 detects the phase of the amplified carrier component whichis indicative of the logical state of data that is scanned. The phasedetector is “locked in” to a modulation phase reference. Operation ofthe amplifier 332 and the phase detector 336 at the carrier frequencyrather than the baseband frequency provide a noise resistant channel anda greatly increased number of samples per data bit to reduce bit errorrate. The phase detector 336 provides a phase detector output 338. Thephase detector output 338 is couplable to a read channel decoder thatprovides error detection and correction before passing data on to a hostcomputer system. In one aspect, the phase detector also provides areliability or probability output that indicates the probability ofaccuracy of each output bit from the phase detector. The probabilityoutput can be coupled to the read channel and used in the errorcorrection process.

In one aspect the oscillatory component of the mechanical contact force307 is generated by a microactuator 350. An oscillator 354 provides anelectrical drive 352 to the microactuator 350. The oscillator 354 iscontrollable by a read mode command 356. The oscillator can beselectively activated during the read mode, and shut off during a writemode. In one aspect, the oscillator 354 is a VFO that is synchronized torun at a multiple of the baseband bit rate. The microactuator 350 cancomprise any suitable microactuator that provides the desired level ofoscillatory force and can comprise an electrostatic actuator, apiezoelectric actuator, a magnetostrictive actuator, or other known typeof microactuator.

FIG. 4 illustrates an exemplary timing diagram 400 correspondinggenerally with the apparatus 300 shown in FIG. 3. In FIG. 4, horizontalaxes represent time and vertical axes represent amplitudes. The timingdiagram includes graphical representations of the electrical read modecommand (356 in FIG. 3), the mechanical electrode force (307 in FIG. 3),the direction of polarization of the storage media 302 under theelectrode tip 308, the carrier component of voltage amplitude sensed atthe electrode tip 308 and present on line 330, and the phase of thecarrier component on line 330. It is understood by those skilled in theart that timing diagrams show timing relationships between multiplesignals in a system, and that actual measurements of a system willinclude noise and other artifacts that may not be explicitly illustratedin a timing diagram.

At time 402, the read mode command 356 changes from a first logic state404 to a second logic state 406, indicating that the apparatus 300 isstarting a READ mode of operation. The oscillator 354, responsive to thesecond logic state 406, begins providing the oscillatory electricaldrive 352 to the microactuator 350.

Up until the time 402, the mechanical contact force 307 includes only aconstant mechanical force component 408, which is represented by astraight line. After time 402, the mechanical contact force 307 includesboth a constant mechanical force component and a modulated forcecomponent which is represented by oscillator line 410 which is offsetfrom zero by the level of the constant mechanical force component 408.In one aspect, the constant mechanical force component is larger thanthe modulated force component, and the total contact force does not dropto zero at any time during the oscillation.

The storage media 302 under the electrode tip 308 is polarized in one oftwo directions under the electrode tip 308 as illustrated at 412 in FIG.4. The storage media has polarization direction transitions at times414, 416, 418, 420. There is no polarization direction transition,however, at time 422.

The storage media 302 under the electrode tip 308 is piezoelectric, andgenerates a piezoelectric voltage that is sensed by electrode tip 308.The piezoelectric voltage is a function of the amplitude of themechanical contact force 307 and also has a phase that is a function ofthe direction of the polarization under the electrode tip 308.

The voltage at electrode tip 308 includes a carrier component 430. Thecarrier component 430 has a phase 440 (relative to the electrode force)and the phase 440 has phase transitions at times 432, 434, 436, 438. Thephase transitions 432, 434, 436, 438 correspond with polarization phasetransitions 414, 416, 418, 420.

FIG. 5 illustrates a block diagram of a data storage apparatus 500. Datastorage apparatus 500 is similar to data storage apparatus 300 in manyrespects. Reference numbers used in FIG. 5 that are the same asreference number used in FIG. 3 identify the same or similar features.

In FIG. 5, a unity gain buffer amplifier 502 is provided. The input ofamplifier 502 is coupled to the electrode 306. The output of amplifier502 is coupled along line 514 to A/D converter 512. The output ofamplifier 502 is connected to a shield 504 that substantially surroundsthe electrode 306 as illustrated. The amplifier 502 has a gain of 1 (orslightly less than 1). The shield 504 is driven by the amplifier 514 tohave substantially the same potential as the electrode 306. Thisarrangement is referred to as a driven shield (also called drivenscreen) and effectively reduced stray capacitance between the electrode306 and the surrounding environment. The amplifier 514 has a lowimpedance output such that coupling of noise to line 514 from theenvironment is loaded by low impedance output, and voltage noise at theinput of A/D converter 512 is reduced. A/D converter 512 can be abitstream converter, a delta sigma converter or other known type of A/Dconverter. An A/D converter output 516 is coupled to a digital filter506. Digital filter 506 has a narrow passband centered around thecarrier frequency Fo. An Fo reference output 510 is coupled to thedigital filter 506. The digital filter 506 provides a digital filteroutput 508 that couples to a phase synchronization detector 336. Thephase synchronization detector 336 receives the Fo modulation phasereference output 510 which serves as a modulation phase reference.

In other respects, the apparatus 500 is similar to the apparatus 300.Features disclosed with respect to one of the apparatus 200, 300, 500can be used or appropriately adapted for use with another one of theapparatus 200, 300 and 500.

FIG. 6 illustrates a graph of charges that are piezoelectricallyproduced by forces from static (non-scanned) nanoindentation electrodeson ferroelectric thin film layers. The data shown in FIG. 6 is knownfrom V. Koval et al., J. Appl. Phys., 97, 074301, 2005. A vertical axis602 represents charge in picocoulombs. A horizontal axis 604 representsapplied force in millinewtons.

A dashed line 606 represents charge produced by increasing force to fromnear zero up to 500 millinewtons and then decreasing the force back tonear zero force. For dashed line 606, a 700 nanometer thin filmferroelectric layer is considered to be in a random initial condition ofslight negative polarization. A charge of about −5 picocoulombs isproduced as illustrated.

After completion of the force application cycle represented by dashedline 606, the 700 nanometer thin film is next positively polarized.After completion of the positive polarization process, a force on ananoindentation electrode is increased from near zero up to 500millinewtons and then is decreased to near zero force. As illustrated bydotted line 608, the charge produced is approximately +18 picocoulombs.

As illustrated by line 610, a charge of approximately +12 picocoulombsis produced by a positively charged layer with a thickness of 70nanometers.

The charge Q that is piezoelectrically generated in response to a force,F, due to the piezoelectric response of a material with a piezoelectriccoefficient d, is approximately:Q=dF.  Equation 1

The capacitance C of a parallel plate capacitor with area A, filled witha dielectric of the thickness D and dielectric constant ∈, is given by:C= _(∈)∈_(o) A/D.  Equation 2

If a charge is placed on a capacitor, a voltage U=Q/C will result.Therefore, the voltage signal is given by:U=Q/C=(dF)/(_(∈)∈_(o) A/D)=(dfD)/(_(∈)∈_(o) A).  Equation 3

The force used to press the tip of an AFM onto the sample in contactmode could be up to 100 nanonewtons (nN). A typical contact area of anAFM tip is 400 square nanometers (nm²). For BaTiO₃, d is approximately86 picocoulombs per newton (pC/N) and ∈=170.

The released charge, for D=40 nm, is estimated to be 8.6×10⁻¹⁸ C (about54 electrons) and would result in a voltage signal of +/−0.6 V. Thisvoltage signal is obtained when capacitive loading from a voltagemeasurement circuit is negligible. The sign of the voltage signaldepends on whether the direction of the polarization is opposed to or inthe same direction as the pressure and therefore allows the detection ofthe polarization state.

It is to be understood that even though numerous characteristics andadvantages of various aspects of the invention have been set forth inthe foregoing description, together with details of the structure andfunction of various aspects of the invention, this disclosure isillustrative only, and changes may be made in detail, especially inmatters of structure and arrangement of parts within the principles ofthe present invention to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed. Forexample, the particular elements may vary depending on the particularapplication for the piezoelectric reading system while maintainingsubstantially the same functionality without departing from the scopeand spirit of the present invention.

1. An apparatus, comprising: data storage media with a scannablesurface; an electrode contacting the scannable surface with a contactforce; and the data storage media generating a baseband piezoelectricpotential that is picked up by the electrode.
 2. The apparatus of claim1, wherein the baseband potential has a polarity that varies as afunction of data polarity on the data storage media.
 3. The apparatus ofclaim 2, comprising: a read circuit coupled to the electrode thatreceives the baseband potential and provides a read circuit output thatis representative of the phase.
 4. The apparatus of claim 3 wherein theelectrode comprises an electrostatic shield and the read circuitcomprises a unity gain amplifier with an amplifier input coupled to theelectrode and an amplifier output driving the electrostatic shield toreduce stray capacitance of the electrode.
 5. The apparatus of claim 3wherein the read circuit comprises an analog-to-digital convertercoupled to the electrode.
 6. The apparatus of claim 1, comprising: anactuator modulating the contact force with a modulation force, the datastorage media generating a modulated potential that is picked up by theelectrode.
 7. The apparatus of claim 6 wherein the actuator iscontrollable by a read command.
 8. The apparatus of claim 1 comprisingan array of spaced apart electrodes that contact multiple locations onthe scannable surface.
 9. The apparatus of claim 6 wherein the actuatorcomprises a piezoelectric microactuator.
 10. The apparatus of claim 9and further comprising an oscillator providing an oscillatory electricaloutput to the actuator.
 11. A method, comprising: providing a scannableferroelectric data storage surface and a scanning electrode contactingthe storage surface with a contact force; sensing a piezoelectricvoltage that is generated at the storage surface by the contact force;and detecting data stored on the storage media as a function of thepolarity of the sensed piezoelectric voltage.
 12. The method of claim 11wherein the sensed piezoelectric voltage comprises a basebandpiezoelectric voltage.
 13. The method of claim 11 and modulating thecontact force to generate a modulated piezoelectric voltage.
 14. Themethod of claim 11 and shielding the contact electrode with a shieldthat is driven at substantially the sensed piezoelectric voltage. 15.The method of claim 11 and amplifying the sensed piezoelectric voltagewith an amplifier.
 16. The method of claim 11 and controlling thecontact force with a read command.
 17. A circuit, comprising: aferroelectric electrode scanning system having data stored thereon witha data polarity, the scanning system generating a piezoelectricpotential as a function of the data polarity; an amplifier receiving thepiezoelectric potential and providing an amplified output; and adetector receiving the amplified output and generating a detector outputindicating the data polarity.
 18. The circuit of claim 17 comprising amicroactuator modulating a scanning force and the detector demodulatingthe amplified output.
 19. The circuit of claim 17 comprising: aelectrostatic shield that shields the piezoelectric potential.
 20. Thecircuit of claim 17 wherein the detector comprises a modulation phasedetector.